1. Field of the Invention
The present invention relates to a magnetic head having a slider which is adapted to be mounted on a device such as a hard disc device. In particular, this invention relates to a magnetic head capable of reducing a spacing loss by directly forming a carbon film on the surfaces of core layers of a thin film element provided on the above slider. The present invention also relates to a method for manufacturing such an improved magnetic head.
2. Description of the Related Art
FIG. 4 is a cross sectional view indicating a conventional magnetic head adapted to be mounted on a hard disc device, with its surface facing upward (facing a recording medium).
Referring to FIG. 4, the magnetic head 4 involves an upstream side A and a downstream side B (when viewed along the discs moving direction), with the upstream side A referred to as leading side and the downstream side B as trailing side.
In FIG. 4, a reference numeral 1 represents a slider formed by a ceramic material. On its surface facing a recording medium, there is formed a recording medium facing surface 5 (an upwardly floating surface serving as an air bearing surface). As shown in FIG. 4, the recording medium facing surface 5 is formed into a crown-like shape having a predetermined curvature. Further, adjacent to the leading side A of the recording medium facing surface 5, there is formed an inclined surface 6.
Referring again to FIG. 4, in connection with an end portion 2 on the trailing side B of the slider 1, there is provided a protective layer 8 within which is further formed a thin film element 3, so that the thin film element 3 is completely covered by the protective layer 8. The structure of the thin film element 3 will be explained in detail later.
As shown in FIG. 4, on the recording medium facing surface 5 and on surface II (facing the recording medium) of the thin film element 3, there is formed a base layer 9 made of a material such as SiO2 or Si. Further, a carbon film 10 is formed on the base layer 9.
Here, the carbon film 10 serves as a protective layer for the magnetic head. Therefore, by forming the carbon film 10, it is possible to prevent the surface of the thin film element 3 from getting corroded. In addition, the provision of the carbon film 10 is proved to be effective for reducing an abrasion of the surface of the thin film element 3 and the recording medium facing surface 5, even if there is a possible collision between the magnetic head and a recording medium.
FIG. 2 is a perspective view indicating the structure of the thin film element 3 provided at an end portion 2 on the trailing side of the slider 1. However, in FIG. 2 there are not shown the base layer 9, the carbon film 10 and the protective layer 8, though they are shown in FIG. 4.
Referring to FIG. 2, at an end portion 2 on the trailing side of the slider 1, there is formed a lower shield layer 11 consisting of a NiFe alloy (permalloy). Formed on the lower shield layer 11 is a magneto-resistive effect element layer 12, with a lower gap layer (not shown) formed therebetween. Further, formed on the magneto-resistive effect element layer 12 is a lower core layer 13 (serving as an upper shield layer) consisting of NiFe alloy, with an upper shield layer (not shown) formed therebetween.
On the lower core layer 13 is spirally formed a coil layer 14 with a gap layer (not shown) formed therebetween. In addition, an upper core layer 15 is formed on the coil layer 14, with an insulating layer (not shown) formed therebetween. However, the upper core layer 15 is also formed by a magnetic material such as a NiFe alloy, just as the lower core layer 13.
Referring again to FIG. 2, a front end portion of the upper core layer 15 is facing the lower core layer 13, with a magnetic gap G formed therebetween. Further, a base end portion 15a of the upper core layer 15 is in contact with the lower core layer 13.
As is understood from FIG. 2, the thin film element 3 is an MR head (a read-out head), in which a multi-laminated structure arranging from the lower shield layer 11 to the lower core layer 13 (an upper shield layer) employs an magneto-resistive effect element so as to detect a leaked magnetic field leaking from a recording medium such as a hard disc. Further, on the MR head is laminated an inductive magnetic head (a write-in head) formed by another multi-laminated structure arranging from the lower core layer 13 to the upper core layer 15.
Referring to FIG. 4, the slider 1 of the magnetic head is supported by a flexure (not shown) which itself is fixed on a front end of a load beam (not shown). Effected by a resilient force of the load beam which has been formed as a plate spring, the slider 1 is forced to be urged towards a recording medium such as a hard disc. Such a magnetic head is usually used in a hard disc device capable of operating in a contact/start/stop manner, so that when the hard disc is in its stopped state, the recording medium facing surface 5 of the slider 1 will get in contact with the recording surface of the hard disc, effected by the above resilient force. On the other hand, once the hard disc begins to move, an air flow will be directed to flow in the disc's moving direction, passing through a space formed between the slider 1 and the surface of the disc. Thus, the recording medium facing surface 5 will receive an upwardly floating force caused by the air flow, rendering the slider 1 itself to float upwardly a short distance from the surface of the disc.
When in an upwardly floating condition, the slider 1 will be in an inclined position in a manner such that its leading side A is higher than its trailing side B. Further, when in such an upwardly floating condition, information is allowed to be recorded on the disc, by virtue of a leaked magnetic field formed between the lower core layer 13 and the upper core layer 15 of the thin film element 3 (shown in FIG. 2). Alternatively, magnetic signals from the disc may be detected by virtue of the magneto-resistive effect element layer 12 of the thin film element 3.
With the prior art discussed above, a base layer 9 is involved in the magnetic head so that a carbon film 10 (serving as a protective layer) is formed through the base layer 9 on the recording medium facing surface 5 and the surface of the thin film element 3. If the carbon film 10 is directly formed on the thin film element 3 without the base layer 9 formed therebetween, a formed carbon film 10 will separate (peel) from the thin film element 3, or at least it is difficult to obtain a uniformly formed carbon film without any irregular convex and concave points or spots.
The above problem is caused due to a crystal structure forming the surfaces of the core layers of the thin film element 3. As discussed above, both the lower core layer 13 and the upper core layer 15 are formed by a NiFe alloy. However, upon checking the crystal structures of both the layers 13 and 15 by means of X-ray diffraction, it was found that the interior portions of the layers 13 and 15 are mainly .gamma. phase (face centered cubic lattice), while the surface potions of the two layers 13 and 15 are mainly .alpha. phase (body centered cubic lattice). In fact, the a phase is a surface layer having a considerable thickness, with its largest thickness being 200 .mu.m.
Since the surface structures of the lower core layer 13 and the upper core layer 15 involve .alpha. phase having a considerable thickness, when the carbon film 10 is directly formed on the surfaces of the core layers 13 and 15, there will occur an abnormal diffusion between the .alpha. phase and the carbon film 10. For this reason, it is difficult to obtain a carbon film having a uniform thickness, and it is likely that a formed carbon film will separate (peel) from the surfaces of the core layers 13 and 15.
Moreover, if the surface structures of the lower core layer 13 and the upper core layer 15 involve .alpha. phase having a considerable thickness, an undesired spacing loss will become large, resulting in a low efficiency of a magnetic field (which is necessary for information recording).
The reason causing the above problem may be concluded to the following fact. Namely, the .gamma. phases of the core layers 13 an 15 will substantially function as a core layer, whilst the .alpha. phases forming the surface structures of the core layers 13 and 15 fail to function as a core layer. For this reason, the .alpha. phase will cause a spacing loss. As a result, the thicker the .alpha. phase, the larger the spacing loss will be.